A union can negotiate with every employer even if they have only one member working there. The union needn't be elected to do so: they just represent their members.

Fake unions play a role in temporary work: These slave traders must pay the same wage as the company where the slaves actually work IF THEY DON'T HAVE AN AGREEMENT OF THEIR OWN. So they have fake agreements with fake unions. They get away with it, because so few temp workers are organised in real unions

Worker councils are elected in the companies, but they don't do bargaining and they are banned by law from calling to strike.